Automatic controller



Oct. 12 ,1926.

C. l. HALL AUTOMATI C C ONTROLLER Filed Jan. 4. 1922 Irv/enter" ChesterI. Hall, y His Attorney.

Patented Oct. 12, 1926.

UNITED STATES PATENT. OFFICE.-

CHESTER 1. BALL, or rear WAYNE, INDIANA, assren'oa ro GENERAL ELECTRICcomm, a. conrona'rron or NEW Yon]:-

AUTOMATIC CONTROLLER.

. Application fled January 4, 1922. Serial No. 526,994.

My invention relates to automatic controlling devices and its principalob'ect is to provide a controlling device whic may be set to operateafter an interval, together with means for modifying the intervalaccording to a variable of an electric circuit. -A more specific objectof my invention is to provide an automatic device for opening anelectric circuit, which device may be set to operate at time intervalswhich are inversely proportional tothe square of the voltage of thecircuit. Certain other .features of my invention are applicable to timeswitches in general as will appear as the description proceeds.

The features of my invention which I believe to be novel will be pointedout in the appended claims. The details of construction and the methodof operating a switch in accordance with my invention will be understoodfrom the following description taken in connection with the accompanyingdrawing. 4

In the following description I have chosen to illustrate my invention asa device for timing the duration of an X-ray exposure in X-ray apparatusof the type shown in the copending application of William D. Coolidgefor X-ray apparatus, Serial No. 395,088, filed July 9, 1920 and assignedto the same assignee as this invention. The X-ray efi'ect produced by atimed exposure will depend upon the square of the voltage applied to theterminals of the X-ray tube. If this voltage is' variable, it isimportant that the time of exposure be inversely proportional to thesquare of the voltage if consistent and accurate results are to beobtained. In the application of my invention I provide an electricmotor, the speed of which is proportional to the square of the appliedvoltage, for opening the circuit of the X-ray tube after an intervalwhich is proportional to the time required for a given exposure underconditions of normal voltage modified by the actual voltage conditions.

Referring now to the drawin 1 indicates an X-ray tube which is sup liewith energy through the transfogmer 2 rom supply lines 3. One terminalof the transformer primary is connected to one side of the supplythrough wire 4 and the other primary terminal is connected to theopposite side of the line through wire 5, automatic time switch 6, wire7, manual starting switch 8 and wire 9. The inverse voltage squaredtiming device for controlling the switch 6 consists essentially of twoparts; first a motor designated in general by the numeral 10, the speedof which is directly proportional to the square of the applied voltage,and second; a train of gears designated in general by the numeral 11,which is arranged so that it may be "placed in driving connection withthe motor. The motor 10 is similar in operation to the well knowninduction watthour meter and consists of a disc 12 of conductingmaterial such as copper rotatably mounted in the air gap formed betweenthe magnetic pieces 13 and 14. The magnetic piece 13 comprises the coreof two reactive coils 15 and 16 connected in series across the supplysupplies the X-ray tube 1. The shifting magnetic field produced by theinteractionof these magnetic structure's sets u currents in the copperdisc 12 and causes t e same to rotate in a well understood manner. Dragmagnets 18 of the proper strength are provided to limit the speed of thedisc 12 to the proper value by imposing a load thereon directlyproportional to the speed of the disc. The combination of the torqueproducing element and the drag magnet causes the disc to rotate ataspeed directlyproportional to the square of the voltage of the source3. Since in the present case an alternating current source of supply isprovided tor the X-ray tube, the motorelement is an alternating currentmotor. However, it will be understood that a direct current motor havingsimilar speed-voltage characteristics may be rovided in cases where thetranslating device to be controlled is supplied from a direct currentsource. The disc 12 is mean tsuitable bearings not shown.

23 carries a gear 24 meshing with the switch operating gear 25. One ofthe contacts of the switch 6, which is normally closed, is carried on aspring arm '26 which stands in the path of movement of the upper end ofa pin 27-carried by the gear 25, so that when the pin 27 is moved intocontact with the arm 26 by the rotation of gear 25 in the directionshown by the arrow, the switch contact 6 will be separated and theswitch opened. The directions of rotation of the motor element and thevarious gears for accomplishing this result are shown bythe arrows. Theear train is normally disengaged from t e spur gear 20 as illustrated.When the gear 21 is brought into engagement with spur gear 20, in amanner to be explained presently, the in 27 will be rotated against arm26 and t e switch6 opened. The gears arearranged so that just after theswitch 6 has been opened the mutilated or blank portion 22 of the gear21 comes opposite spur gear 20 and further rotation of the gear traincomprising gears 21, 24 and 25 is prevented. The shafts 23 and 28 whichcarry the last mentioned portion of the gear train are mounted in amovable structure comprising a pair of parallel plates one of which isshown at 29, the upper plate being omitted for the purpose of exposingthe parts of the switch operating mechanism. This structure, which willhereafter be referred to as the plate 29, is pivoted at 30 so as to beswung in a plane perpendicular to the motor shaft 19. The plate 29 isnormally held against a stop 31 by means of a spring 32 with the gears20 and 21 out of engagement. The plate 29 also carries a support for theswitch contacts 6. The plate 29 carries the armature 33 of anelectromagnet 34, the operating coil 35 of which is adapted to be closedby the switch 8 to connect this coil across the source of supply 3. Thearmature 33 is normally held away from its seat by the spring 32,butwhen the switch 8 is closedthe electromagnet 34 draws its armature 33toits seat, swinging plate 29 on its pivot 30 to bring gear 21 intodriving engagement with gear 20, thereby placing motor 10 in drivingconnection with the switch operating mechanism.

In order that the operation of the switch 6 may be timed to give anexposure of a predetermined definite value, means are provided forsetting the switch operating gears in a position to bring pin 27 adefinite distance away from arm'26. This setting means comprises a stoparm 36 (provided with a pointer 37. This pointer an stop arm are pivotedaround the lower end of shaft 28 so that the stop 36 is in the path ofmovement of the lower end of switch 0 erating pin 27 and the outer endof the pointer cooperates with a scale 38 on plate 29. This pointer 37and stop arm 36 may be rotated around shaft 28 and is provided withfriction means for holding it in any position to which it may beadjusted. When the gears 20 and 21 are out of engagement the switchoperating gear train is rotatably biased in the opposite direction tothat in which it isdriven by the motor, by means of the light spiralspring 39. The inner end of this spring is fastened to the shaft 28 andits outer end to a stationary pin 40 held in the movable plate 29. Thuswhen the gear train is disengaged from the pinion 20 the pin 27 is heldagainst stop 36, and by moving the pointer 37 about its pivot the switchoperating gear train'is rotated and the pin 27 may be set any desireddistance away from the arm 26. The scale 38is calibrated and marked insuitable units which correspond to the time required tooperate theswitch 6 after the switch 8 has been closed under conditions of normalvoltage. This scale might also be calibrated in values of X-rayexposure. The left hand end of the scale corresponds to zero time and ifthe pointer 37 is moved to that point from the position'shown, the stop36 will move pin 27 into contact with arm 26 so that any furthermovement of pin 27 in the same direction will cause the switch 6 toopen. If each division of the scale represents 10 seconds the settingshown in the illustration is such that the switch 6 will be opened 40seconds after switch 8 is closed, provided the voltage supplied to themotor remains normal during the interval. It the voltage is abovenormal, however, the motor speed will be faster and the switch will teopened quicker. In like manner, it'the voltage is low, the motor willrun slower and the switch will remain closed a longer time. As has beenpreviously pointed out the motor 10 is designed to have a speedproportional to the square of the applied voltage, consequently, thetime during which the switch 6 and the circuit of the primary oftransformer 2 remains closed,.will be inversely proportional to thesquare of the applied voltage for any given setting.

A complete cycle of operation will now be explained: Assuming the partsare-in the position shown, the line switch 41 is first closed energizinmotor 10 which immediately starts in the direction of the arrow on thedisc 12 and runs at a speed proportional to the square of the voltage.The pointer 37 is then moved to the point on the scale corresponding tothe value of the exposure desired. This movement will cause the pin 27to be moved 9. correspond ing distance away from arm 26 and themutilated portion 22 of the gear 21 a corresponding distance away from aposition opposite pinion 20. The apparatus is now in condition to takethe exposure which is started by the closing of switch 8 which completesthe supplied circuit comprising coductor 4, transformer 2, conductor 5,switch 6, conductor 7, switch 8 and conductor 9. \Vhen switch 8 isclosed two things happen; first, the primary transformer 2 is energizedand the X-ray discharge takes place in the tube 1; second, the circuitof operating coil 35 of electromagnet 34 is closed causing its armature33 to be drawn to its seat, rotating plate 29 about pivot 30 andbringing the gear 21 into engagement with the pinion 20, the latter ofwhich is now being driven by the motor 10. The switch operating geartrain is now driven in the direction shown by the arrows and pin 27approaches arm 26 at the same time the mutilated portion 22 of gear 21approaches pinion 20, at speeds proportional to the square of thevoltage which happens to exist on the supply lines at this time.

This same voltage is also supplied to the.

primary of transformer 2 so that the switch 6 is opened at just theright instant to give the correct exposure irrespective of the voltage.Immediately thereafter, the mutilated portion 22 runs into the piniongear 20 and the gear train stops. The operator may then open the switch8 at his leisure which causes the deenergizing of the electromagnet 34.The spring 32 then swings the plate 29 about pivot 30 disengaging thegear train from pinion 20 which is immediately rotated by spring 39 intoa position determined by the setting of the pointer 37 and the apparatusis ready for another exposure. It will be noticed that the mutilatedportion 22 not only stops the gear 'train after the switch 6 has beenopened but also prevents this switch from being closed again until thecircuit has been opened at 8. By means of this apparatus an unskilledoperator may obtain accurate and consistent results without danger tothe patient or the X ray tube such as might be caused by excessivevoltages. After the operator has once adjusted the pointer 37 and closedthe switch 8, he may devote his entire attention to his patient withoutbeing bothered by watching a voltmeter or watch. The motor operatedswitch also prevents an underexposure, by prolonging the time thedesired amount when the voltage is below normal.

My invention has been illustrated in connection with a motor having aspeed characteristic which is directly proportional to the square of thevoltage. However, it will be understood that in certain cases the natureof the load might be such that it would be desirable to. open or controlthe circuit in a time directly or inversely proportional to some othervariable such as the first power of the voltage, the frequency, thecurrent consumed by the load itself, etc in which case I would designthe motor with the proper speed characteristic to produce the desiredresult.

Although I have illustrated my invention in'connection\with analternating current source and an X-ray tube, it will be evidentthat thesame operating mechanism might be used with a direct current motor ofthe watt hour type to control the operation of an electric heatingcircuit, for example, and the contacts at 6 might control the operatingswitch of such a circuit through a relay or relays where the current tobe controlled is heavy or the voltage too high to be broken directly. Byproviding an automatic line switch in series with switch 41 controlledthrough a relay from the contacts 6, I might dispense with theelectromagnet 34 and the disengaging feature of the gears and shut themotor down at the same time the circuit of the tube is opened, in whichcase the motor would be started simultaneously with the exposure byclosing the switch 41. In some cases it mightbe desirable to provide twoor more sets of contacts similar to the one shown at 6 arranged to beprogressively'oper ated by the same switch operating means.

In accordance with the provisions of the patent statutes, I havedescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodiment thereof;but I desire to have it understood that the apparatus shown is onlyillustrative and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. A timelimit circuit controller comprising a switch, an operatingmechanism therefor adapted to be moved in one direction to actuate theswitch to one position, a motor for actuating the mechanism, means formoving the mechanism in the opposite direction to allow the switch tomove to another position, a normally disengaged gear 7 drive between themotor and the mechanism,

means for engaging the gear drive comprising an electromagnet, and meansarranged after the switch has been actuated by said motor operatedmechanism to prevent further movement of the mechanism While the motorand the electromagnet are energized in one direction to open the switch,resilient means for moving the mechanism in the op posite direction toallow the switch to close, an induction disc motor for moving themechanism in the direction to open the switch, a normally disengagedgear drive between the motor and the mechanism, on electromagnet havinga pivoted armature arranged on movement to the attracted position toeffect the engagement of the gear drive, and means arranged after theswitch is opened to prevent further movement of the mechanism in theswitch opening direction while the motor and the electromagnet areenergized comprising a blank portion in one of the gears of the drivingconnection. In witness whereof, I have hereunto set my hand. this 29thday of December, 1921.

CHESTER I. HALL

